20s Plenty for Us

Why reduce speeds in our residential streets?
There are a whole host of reasons but in climate emergency terms it is to enable people to travel in the safest, healthiest and greenest way that we know and that is by cycling. We know that people will cycle if they feel safe.  The way to do this is to provide cycle ways separate from the carriageway – as opposed to a narrow lane in the kerb; and, on our side streets to have speed limits set below 20mph.

Just imagine the difference if all our secondary children could walk or cycle to their local school.  Of course, we would be reducing air pollution too.

Why is 20mph so important for safety?

Studies show that humans react differently when they are moving below 20mph as opposed to when they are moving above that speed.  It is all to do with our own maximum sprinting speed.  For obvious reasons, evolution did not equip us to react to situations when we were travelling faster than we could sprint.  So when travelling below 20mph we can deal with other drivers, pedestrians and cyclists in a far more convivial manner than when we are travelling above that speed.  

We have 30mph now - is that not good enough?

When the urban speed limit was set at 30mph in 1934 it was a matter of judgement that is was a safer speed.  Via a great deal of research, we now know that at above roughly 22mph most people find it difficult to read the intention of the person coming towards us.  The lower our speed, the more likely it would be that we could avoid bumping or crashing into someone. 

But we know driving slower is safer – what is so special about 20mph?
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Unlike braking distance, which increases with speed gradually, the ability to read the intention of a person coming toward you declines slowly up to around 20mph and then collapses rapidly.  Below that speed, you can see where the other person is looking and act accordingly.  Above that speed, you have to guess – and guess very quickly - to avoid a crash or, more seriously, injury or death.

The police cannot enforce a 20mph speed limit – so what is the point?

It is regrettable that our police service is decidedly overstretched but just because our police cannot, at the moment, enforce the speed this does not mean a 20mph limit should not be introduced.  Otherwise we might as well abolish the crime of theft.